US20230174390A1 - Method for controlling fresh water generation apparatus by estimating filtration property, method for determining presence of trouble in fresh water generation apparatus, fresh water generation apparatus, program for operating fresh water generation apparatus, program for determining presence of trouble in fresh water generation apparatus, and recording medium - Google Patents

Method for controlling fresh water generation apparatus by estimating filtration property, method for determining presence of trouble in fresh water generation apparatus, fresh water generation apparatus, program for operating fresh water generation apparatus, program for determining presence of trouble in fresh water generation apparatus, and recording medium Download PDF

Info

Publication number
US20230174390A1
US20230174390A1 US17/798,982 US202117798982A US2023174390A1 US 20230174390 A1 US20230174390 A1 US 20230174390A1 US 202117798982 A US202117798982 A US 202117798982A US 2023174390 A1 US2023174390 A1 US 2023174390A1
Authority
US
United States
Prior art keywords
water treatment
treatment method
stage water
stage
filtration
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
US17/798,982
Other languages
English (en)
Inventor
Kazunori Tomioka
Kazuki Hagawa
Hiroshi Hamada
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toray Industries Inc
Original Assignee
Toray Industries Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toray Industries Inc filed Critical Toray Industries Inc
Assigned to TORAY INDUSTRIES, INC. reassignment TORAY INDUSTRIES, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HAMADA, HIROSHI, HAGAWA, Kazuki, TOMIOKA, KAZUNORI
Publication of US20230174390A1 publication Critical patent/US20230174390A1/en
Pending legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/008—Control or steering systems not provided for elsewhere in subclass C02F
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/58—Multistep processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/26—Further operations combined with membrane separation processes
    • B01D2311/2642—Aggregation, sedimentation, flocculation, precipitation or coagulation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/70—Control means using a programmable logic controller [PLC] or a computer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2317/00—Membrane module arrangements within a plant or an apparatus
    • B01D2317/02—Elements in series
    • B01D2317/025—Permeate series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/12—Controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/22—Controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/001—Upstream control, i.e. monitoring for predictive control
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/005—Processes using a programmable logic controller [PLC]
    • C02F2209/006—Processes using a programmable logic controller [PLC] comprising a software program or a logic diagram
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/44—Time
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/16—Regeneration of sorbents, filters

Definitions

  • the present invention relates to a method of controlling a fresh-water production apparatus for obtaining treated water by treating natural water, such as river water, lake water, or seawater, sewage, wastewater, or industrial wastewater, on the basis of a prediction of filtration characteristics of the fresh-water production apparatus, a trouble assessment method for a fresh-water production apparatus, a fresh-water production apparatus, an operation program for a fresh-water production apparatus, a trouble assessment program for a fresh-water production apparatus, and a storage medium.
  • natural water such as river water, lake water, or seawater
  • water treatment methods including settling/floatation separation, an anaerobic treatment method, a sand filtration method, a membrane filtration method, an ion exchange method, a physical adsorption method, and an oxidation/disinfection method, and one or more of these water treatment methods are selected or used in combination in accordance with the properties of the raw water and use of the water to be produced.
  • membrane separation methods are increasingly used in various fields because of advantages thereof including energy/space saving and improvements in the quality of treated water. Examples thereof include application of microfiltration membranes or ultrafiltration membranes to water purification processes for producing industrial water or service water from river water, groundwater, or treated sewage and application of reverse osmosis membranes to seawater desalination. Furthermore, a membrane separation method is coming to be increasingly used in which those separation membranes are used in combination, for example, in such a manner that raw water is filtered with an ultrafiltration membrane and the resultant permeate is treated with a reverse osmosis membrane to thereby obtain clean product water.
  • membrane fouling In the membrane filtration of raw water to be treated, the accumulation of fouling substances on the membrane surface and in pores of the membrane (membrane fouling) proceeds as the amount of the treated water increases, resulting in a change in filtration characteristics, such as a decrease in filtration rate or an increase in filtration pressure.
  • the separation membrane is subjected to physical washing such as: air washing in which bubbles are introduced to the raw-water side of the separation membrane to cause the separation membrane to oscillate and come into contact with itself, thereby scraping away the fouling substances from the membrane surface; or a back-pressure washing (backwashing) in which the treated water or clean water is forcedly passed with pressure in the direction opposite from the direction of the filtration with the separation membrane, thereby removing the fouling substances adherent to the surface of the separation membrane and to the inside of the membrane pores.
  • physical washing such as: air washing in which bubbles are introduced to the raw-water side of the separation membrane to cause the separation membrane to oscillate and come into contact with itself, thereby scraping away the fouling substances from the membrane surface; or a back-pressure washing (backwashing) in which the treated water or clean water is forcedly passed with pressure in the direction opposite from the direction of the filtration with the separation membrane, thereby removing the fouling substances adherent to the surface of the separation membrane and to the inside of the membrane pores.
  • CAB chemical-enhanced backwashing
  • the membrane separation/activated sludge process which is used mainly in sewage treatments, includes a treatment step in which a biological treatment is performed in a biological reaction vessel and the activated sludge is subjected to solid/liquid separation using, for example, a filtration membrane immersed in the reaction vessel, thereby obtaining clean treated water.
  • a biological treatment is performed in a biological reaction vessel and the activated sludge is subjected to solid/liquid separation using, for example, a filtration membrane immersed in the reaction vessel, thereby obtaining clean treated water.
  • solid matter such as some of the activated sludge itself and foreign matter present in the raw water flowing into the reaction vessel, adheres to the surface of the separation membrane and the substances which have adhered cause an increase in membrane filtration resistance.
  • the apparatus is generally operated while preventing or inhibiting fouling, for example, by injecting a chemical such as a scale inhibitor or a bactericide as a measure against fouling or by stopping the filtration and subjecting the upstream portion of the separation membrane to physical washing (flushing).
  • a chemical such as a scale inhibitor or a bactericide
  • the fresh-water production apparatus is generally operated so that the chemical cleaning is conducted at intervals which are as long as possible.
  • Patent Document 1 describes a technique for predicting changes in filtration flow rate using a plurality of operation values in accordance with changes in the raw water to be treated.
  • Patent Document 2 describes a technique for predicting the timing of performing chemical cleaning by predicting the filtration characteristics of the separation membrane using the contents of components of the raw water to be treated.
  • Patent Document 3 describes a technique in which the filtration time for a preceding filtration membrane is changed in accordance with the quality of the raw water to be treated and the filtration rate for a succeeding separation membrane is controlled in accordance with the degree in which the filtration time has been changed.
  • the quality of the raw water is the only factor which is taken into account in changing the filtration time, and the apparatus is not operated while predicting the filtration characteristics or the timing of chemical cleaning. The proposed operation method is hence not useful.
  • An object of the present invention is to provide a method of controlling a fresh-water production apparatus for obtaining treated water by treating natural water, such as river water, lake water, or seawater, sewage, wastewater, or industrial wastewater, on the basis of a prediction of filtration characteristics of a filtration membrane, a trouble assessment method for a fresh-water production apparatus, a fresh-water production apparatus, an operation program for a fresh-water production apparatus, a trouble assessment program for a fresh-water production apparatus, and a storage medium.
  • natural water such as river water, lake water, or seawater
  • a method of controlling a fresh-water production apparatus for treating a raw water in stages by N-stage (N is a natural number of 2 or larger) water treatment methods including:
  • a filtration-characteristic prediction step for an n-th stage (n is any natural number of 2 to N) water treatment method, in which a filtration characteristic of the n-th stage water treatment method is predicted from a predicted input condition for the n-th stage;
  • a filtration-characteristic prediction step for an (n ⁇ 1)-th stage water treatment method in which a filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from a predicted input condition for the (n ⁇ 1)-th stage;
  • a filtration-characteristic deviation assessment step for the n-th stage water treatment method in which a deviation between a predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is assessed;
  • a filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method in which a deviation between a predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed;
  • a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method in which in cases when the deviation has occurred in the filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method, the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method and is recorded;
  • a cyclic prediction calculation step for the n-th stage water treatment method in which the predicted input condition for the n-th stage water treatment method is changed on the basis of the control condition for the (n ⁇ 1)-th stage water treatment method and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the n-th stage water treatment method and is recorded,
  • the fresh-water production apparatus is controlled on the basis of the control condition recording step for the (n ⁇ 1)-th stage water treatment method and the control condition recording step for the n-th stage water treatment method.
  • a method of controlling a fresh-water production apparatus for treating a raw water in stages by N-stage (N is a natural number of 2 or larger) water treatment methods including:
  • a filtration-characteristic prediction step for an n-th stage (n is any natural number of 2 to N) water treatment method, in which a filtration characteristic of the n-th stage water treatment method is predicted from a predicted input condition for the n-th stage;
  • a filtration-characteristic prediction step for an (n ⁇ 1)-th stage water treatment method in which a filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from a predicted input condition for the (n ⁇ 1)-th stage;
  • a filtration-characteristic deviation assessment step for the n-th stage water treatment method in which a deviation between a predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is assessed;
  • a filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method in which a deviation between a predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed;
  • a cyclic prediction calculation step for the n-th stage water treatment method in which in cases when the deviation has occurred in the filtration-characteristic deviation assessment step for the n-th stage water treatment method, the predicted input condition for the n-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the n-th stage water treatment method and is recorded;
  • a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method in which the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed on the basis of the control condition for the n-th stage water treatment method and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method and is recorded,
  • the fresh-water production apparatus is controlled on the basis of the control condition recording step for the (n ⁇ 1)-th stage water treatment method and the control condition recording step for the n-th stage water treatment method.
  • some of a treated water obtained by the (n ⁇ 1)-th stage water treatment method is mixed with a treated water obtained by the n-th stage water treatment method;
  • some of the treated water obtained by the n-th stage water treatment method is mixed with the raw water or with the treated water obtained by the (n ⁇ 1)-th stage water treatment method;
  • some or all of a discharged water from the n-th stage water treatment method is mixed with the raw water or with the treated water obtained by the (n ⁇ 1)-th stage water treatment method;
  • some or all of the discharged water from the n-th stage water treatment method is used as a cleaning water for the (n ⁇ 1)-th stage water treatment method.
  • filtration characteristic is at least one kind of a parameter selected from the group consisting of differential pressure, pure-water permeability, and salt permeability.
  • F at least any of feed-water flow rate, concentrate flow rate, and permeate flow rate, or recovery;
  • G ratio between rates of upstream and downstream permeate discharge (in the case of splitting);
  • a method of trouble assessment for a fresh-water production apparatus including a trouble assessment step in which in N-stage water treatment methods, a trouble in each of the N-stage water treatment methods is assessed from a final predicted input condition obtained in a cyclic prediction calculation step for each of the N-stage water treatment methods.
  • a fresh-water production method including producing fresh water while at least performing either of the following A and B, on the basis of a result obtained by the method of trouble assessment according to any one of (9) to (11):
  • a fresh-water production apparatus for treating a raw water in stages by N-stage (N is a natural number of 2 or larger) water treatment methods including:
  • a filtration-characteristic prediction means for an n-th stage (n is any natural number of 2 to N) water treatment method, in which a filtration characteristic of the n-th stage water treatment method is predicted from a predicted input condition for the n-th stage;
  • a filtration-characteristic prediction means for an (n ⁇ 1)-th stage water treatment method in which a filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from a predicted input condition for the (n ⁇ 1)-th stage;
  • a filtration-characteristic deviation assessment means for the n-th stage water treatment method in which a deviation between a predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is assessed;
  • a filtration-characteristic deviation assessment means for the (n ⁇ 1)-th stage water treatment method in which a deviation between a predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed;
  • a cyclic prediction calculation means for the (n ⁇ 1)-th stage water treatment method in which in cases when the deviation has occurred in the filtration-characteristic deviation assessment means for the (n ⁇ 1)-th stage water treatment method, the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or below a specified value;
  • a control condition recording means for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation means for the (n ⁇ 1)-th stage water treatment method and is recorded;
  • a cyclic prediction calculation means for the n-th stage water treatment method in which the predicted input condition for the n-th stage water treatment method is changed on the basis of the control condition for the (n ⁇ 1)-th stage water treatment method and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method decreases to or below a specified value;
  • control condition recording means for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation means for the n-th stage water treatment method and is recorded;
  • control means of controlling the fresh-water production apparatus on the basis of the control condition recording means for the (n ⁇ 1)-th stage water treatment method and the control condition recording means for the n-th stage water treatment method.
  • a fresh-water production apparatus for treating a raw water in stages by N-stage (N is a natural number of 2 or larger) water treatment methods including:
  • a filtration-characteristic prediction means for an n-th stage (n is any natural number of 2 to N) water treatment method, in which a filtration characteristic of the n-th stage water treatment method is predicted from a predicted input condition for the n-th stage;
  • a filtration-characteristic prediction means for an (n ⁇ 1)-th stage water treatment method in which a filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from a predicted input condition for the (n ⁇ 1)-th stage;
  • a filtration-characteristic deviation assessment means for the n-th stage water treatment method in which a deviation between a predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is assessed;
  • a filtration-characteristic deviation assessment means for the (n ⁇ 1)-th stage water treatment method in which a deviation between a predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed;
  • a cyclic prediction calculation means for the n-th stage water treatment method in which in cases when the deviation has occurred in the filtration-characteristic deviation assessment means for the n-th stage water treatment method, the predicted input condition for the n-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method decreases to or below a specified value;
  • control condition recording means for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation means for the n-th stage water treatment method and is recorded;
  • a cyclic prediction calculation means for the (n ⁇ 1)-th stage water treatment method in which the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed on the basis of the control condition for the n-th stage water treatment method and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or below a specified value;
  • control condition recording means for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation means for the (n ⁇ 1)-th stage water treatment method and is recorded;
  • control means of controlling the fresh-water production apparatus on the basis of the control condition recording means for the (n ⁇ 1)-th stage water treatment method and the control condition recording means for the n-th stage water treatment method.
  • an operation mode selection means which selects an operation mode
  • a cyclic prediction calculation means for each of the N-stage water treatment methods which changes the input condition for filtration-characteristic prediction for each of the N-stage water treatment methods on the basis of the operation mode selected by the operation mode selection means and repeats a prediction calculation until the derivation between a predicted filtration characteristic of each of the N-stage water treatment methods and a filtration characteristic of each of the N-stage water treatment methods decreases to or below a specified value;
  • control means which controls the fresh-water production apparatus on the basis of a control condition recording means for each of the N-stage water treatment methods which determines a control condition for each of the N-stage water treatment methods from a final input condition obtained by the cyclic prediction calculation means for each of the N-stage water treatment methods and records the control condition.
  • some of a treated water obtained by the (n ⁇ 1)-th stage water treatment method is mixed with a treated water obtained by the n-th stage water treatment method;
  • some of the treated water obtained by the n-th stage water treatment method is mixed with the raw water or with the treated water obtained by the (n ⁇ 1)-th stage water treatment method;
  • some or all of a discharged water from the n-th stage water treatment method is mixed with the raw water or with the treated water obtained by the (n ⁇ 1)-th stage water treatment method;
  • some or all of the discharged water from the n-th stage water treatment method is used as cleaning water for the (n ⁇ 1)-th stage water treatment method.
  • the fresh-water production apparatus according to any one of (13) to (16), in which at least any of the N-stage water treatment methods is a membrane separation method and the membrane separation method employs at least one kind of a separation membrane selected from the group consisting of a microfiltration membrane, an ultrafiltration membrane, and a reverse osmosis membrane.
  • F at least any of feed-water flow rate, concentrate flow rate, and permeate flow rate, or recovery;
  • G ratio between rates of upstream and downstream permeate discharge (in the case of splitting);
  • a fresh-water production apparatus including an alarm output/control means which outputs an alarm for a trouble factor or controls the trouble factor, on the basis of a result obtained by the trouble assessment means for each of the N-stages according to (19).
  • a filtration-characteristic prediction step for an n-th stage (n is any natural number of 2 to N) water treatment method, in which a filtration characteristic of the n-th stage water treatment method is predicted from a predicted input condition for the n-th stage;
  • a filtration-characteristic prediction step for an (n ⁇ 1)-th stage water treatment method in which a filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from a predicted input condition for the (n ⁇ 1)-th stage;
  • a filtration-characteristic deviation assessment step for the n-th stage water treatment method in which a deviation between a predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is assessed;
  • a filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method in which a deviation between a predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed;
  • a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method in which in cases when the deviation has occurred in the filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method, the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method and is recorded;
  • a cyclic prediction calculation step for the n-th stage water treatment method in which the predicted input condition for the n-th stage water treatment method is changed on the basis of the control condition for the (n ⁇ 1)-th stage water treatment method and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method decreases to or below a specified value;
  • control condition recording step for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the n-th stage water treatment method and is recorded;
  • control step in which the fresh-water production apparatus is controlled on the basis of the control condition recording step for the (n ⁇ 1)-th stage water treatment method and the control condition recording step for the n-th stage water treatment method.
  • a filtration-characteristic prediction step for an n-th stage (n is any natural number of 2 to N) water treatment method, in which a filtration characteristic of the n-th stage water treatment method is predicted from a predicted input condition for the n-th stage;
  • a filtration-characteristic prediction step for an (n ⁇ 1)-th stage water treatment method in which a filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from a predicted input condition for the (n ⁇ 1)-th stage;
  • a filtration-characteristic deviation assessment step for the n-th stage water treatment method in which a deviation between a predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is assessed;
  • a filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method in which a deviation between a predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed;
  • a cyclic prediction calculation step for the n-th stage water treatment method in which in cases when the deviation has occurred in the filtration-characteristic deviation assessment step for the n-th stage water treatment method, the predicted input condition for the n-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the n-th stage water treatment method and is recorded;
  • a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method in which the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed on the basis of the control condition for the n-th stage water treatment method and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or below a specified value;
  • a control condition recording step for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in the cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method and is recorded;
  • control step in which the fresh-water production apparatus is controlled on the basis of the control condition recording step for the (n ⁇ 1)-th stage water treatment method and the control condition recording step for the n-th stage water treatment method.
  • the operation program for the fresh-water production apparatus having an operation mode selection step for selecting an operation mode, and the operation program causing a computer to execute the following steps in order to operate the fresh-water production apparatus:
  • a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method in which the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed on the basis of an operation mode selected in the operation mode selectin step and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is eliminated;
  • a cyclic prediction calculation step for the n-th stage water treatment method in which the predicted input condition for the n-th stage water treatment method is changed on the basis of the operation mode selected in the operation mode selection step and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is eliminated;
  • a control condition recording step for the (n ⁇ 1)-th stage water treatment method in which a control condition for the (n ⁇ 1)-th stage water treatment method is determined from a final input condition obtained in at least the cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method, of the cyclic prediction calculation steps respectively for the (n ⁇ 1)-th stage water treatment method and the n-th stage water treatment method, and is recorded;
  • the operation program for the fresh-water production apparatus having an operation mode selection step for selecting an operation mode, and the operation program causing a computer to execute the following steps in order to operate the fresh-water production apparatus:
  • a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method in which the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed on the basis of an operation mode selected in the operation mode selectin step and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method is eliminated;
  • a cyclic prediction calculation step for the n-th stage water treatment method in which the predicted input condition for the n-th stage water treatment method is changed on the basis of the operation mode selected in the operation mode selection step and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and the filtration characteristic of the n-th stage water treatment method is eliminated;
  • a control condition recording step for the n-th stage water treatment method in which a control condition for the n-th stage water treatment method is determined from a final input condition obtained in at least the cyclic prediction calculation step for the n-th stage water treatment method, of the cyclic prediction calculation steps respectively for the (n ⁇ 1)-th stage water treatment method and the n-th stage water treatment method, and is recorded;
  • the control condition to be recorded in the control condition recording step for the (n ⁇ 1)-the stage water treatment method is at least one condition selected from the group consisting of the following A to C
  • the control condition to be recorded in the control condition recording step for the n-the stage water treatment method is at least one condition selected from the group consisting of the following F to I
  • the operation program causing a computer to execute a control step in which the fresh-water production apparatus is controlled on the basis of the control condition recording step for the (n ⁇ 1)-th stage water treatment method and the control condition recording step for the n-th stage water treatment method:
  • F at least any of feed-water flow rate, concentrate flow rate, and permeate flow rate, or recovery;
  • G ratio between rates of upstream and downstream permeate discharge (in the case of splitting);
  • a trouble assessment program for a fresh-water production apparatus for treating a raw water in stages by N-stage (N is a natural number of 2 or larger) water treatment methods the trouble assessment program causing, in order to operate the fresh-water production apparatus, a computer to execute a trouble assessment step in which a trouble is assessed from a final predicted input condition obtained in a cyclic prediction calculation step for each of the N-stage water treatment methods.
  • An operation program for a fresh-water production apparatus the program causing a computer to execute at least either of the following steps of A and B, in order to operate the fresh-water production apparatus, in accordance with a result obtained by the trouble assessment program according to any one of (26) to (28):
  • troubles in a fresh-water production apparatus can be extremely easily grasped and measures against the abnormalities can be taken in an early stage. It is hence possible to stably continue the operation while efficiently taking measures against troubles in the fresh-water production apparatus.
  • FIG. 1 is a flowchart showing an example of a fresh-water production apparatus of the present invention.
  • FIG. 2 is a schematic view showing an embodiment of the present invention.
  • FIG. 3 is a schematic view showing another embodiment of the present invention.
  • FIG. 4 is a schematic view showing still another embodiment of the present invention.
  • FIG. 1 An example of the fresh-water production apparatuses of the present invention is, as FIG. 1 shows, a fresh-water production apparatus 7 including: a raw-water tank 1 for retaining raw water to be treated, a first separation membrane device 3 which, in the case where the first water treatment method is a membrane separation method, is for treating the raw water with a first separation membrane to produce treated water, a feed pump 2 for feeding the raw water to the first separation membrane device 3 , a permeate tank 4 for retaining the permeate obtained through filtration by the first separation membrane device 3 , a second separation membrane device 6 which, in the case where the second water treatment method is a membrane separation method, is for further treating the permeate with a second separation membrane, and a high-pressure pump 5 for sending the permeate to the second separation membrane device 6 .
  • a raw-water tank 1 for retaining raw water to be treated
  • a first separation membrane device 3 which, in the case where the first water treatment method is a membrane separation method, is for treating the raw water with
  • the raw water to be treated is a solution to be treated using a water treatment method, and examples thereof include river water, groundwater, seawater, water obtained by sewage treatment, industrial wastewater, and culture broth.
  • the separation membrane used in the first separation membrane device 3 is not particularly limited in the pore diameter thereof so long as the separation membrane is porous.
  • a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane) is used or both are used in combination, in accordance with desired properties of the raw water and water feed rate.
  • MF membrane microfiltration membrane
  • UF membrane ultrafiltration membrane
  • MF membrane microfiltration membrane
  • an MF membrane or a UF membrane may be used in the case where it is desired to remove suspended components, coli bacteria, Cryptosporidium, etc.
  • a UF membrane may be used in the case where it is desired to further remove viruses, high-molecular-weight organic substances, or the like.
  • forms of separation membranes include hollow-fiber membrane, flat membrane, tubular membrane, and monolithic membrane, and any of these may be used.
  • the material of each separation membrane includes at least one member selected from the group consisting of polyethylene, polypropylene, polyacrylonitrile, ethylene/tetrafluoroethylene copolymers, polychlorotrifluoroethylene, polytetrafluoroethylene, poly(vinyl fluoride), tetrafluoroethylene/hexafluoropropylene copolymers, tetrafluoroethylene/perfluoroalkyl vinyl ether copolymers, chlorotrifluoroethylene/ethylene copolymers, poly(vinylidene fluoride), polysulfones, cellulose acetate, poly(vinyl alcohol), polyethersulfones, and inorganic materials such as ceramics.
  • PVDF Poly(vinylidene fluoride)
  • Polyacrylonitrile is more preferred from the standpoint that this polymer has high hydrophilicity and high nonfouling properties.
  • membrane filtration mode either a dead-end filtration type module or a cross flow filtration type may be used, but the dead-end filtration type is preferred because of the small energy consumption thereof.
  • the separation membrane may be either the pressurized type or the immersion type, but the pressurized type is preferred because this type can be operated at a high flow rate.
  • the separation membrane may be either the external-pressure type, in which raw water is fed from the outside of the membrane and a permeate is obtained on the inside thereof, or the internal-pressure type, in which raw water is fed from the inside of the membrane and a permeate is obtained on the outside thereof, but the external-pressure type is preferred from the standpoint of ease of pretreatments.
  • the filtration resistance of the separation membrane i.e., the difference in pressure (differential pressure) between the upstream side and the downstream side of the first separation membrane.
  • a general method of suppressing this increase in differential pressure is to operate the separation membrane device while periodically conducting physical washing so that the filtration and the physical washing are repeated.
  • the filtration is temporarily stopped and a backwashing step, an air washing step, a draining step, and a water feed step are conducted in order.
  • a backwashing step, an air washing step, a draining step, and a water feed step are conducted in order.
  • the backwashing step and the air washing step are simultaneously conducted or the backwashing step is conducted after the draining step or any of those steps is omitted or conducted in two or more times.
  • the backwashing step is a step in which a permeate retained in the permeate tank is caused to flow backward by a backwashing pump (not shown) from the downstream side to the upstream side of the first separation membrane in the direction opposite to the filtration direction to wash the first separation membrane.
  • the back washings which have passed to the upstream side are discharged from the system through a back-washings discharge pipeline. After the backwashing is conducted for a given time period, the backwashing pump is stopped to terminate the backwashing step.
  • the air washing step is a step in which compressed air is supplied with an air washing blower (not shown) to under the first separation membrane to oscillate and thereby wash the separation membrane. After the air washing is conducted for a given time period, the air washing blower is stopped to terminate the air washing.
  • the air supplier may be either a blower or a compressor. In the case of a compressor, however, it is preferable that the compressor is of the oil-free type so that an oil is not supplied to the separation membrane via the air.
  • the draining step is a step in which the suspended components removed from the first separation membrane in the backwashing step and air washing step are discharged from the system.
  • the suspended components are discharged from the system through a drainage pipeline connected to under the first separation membrane. After the draining is conducted for a given time period, the draining step is terminated.
  • the water feed step is a step in which after the draining step, raw water to be treated is fed to the upstream side of the first separation membrane.
  • the raw water is fed to the upstream side of the first separation membrane with the feed pump 2 , and after the upstream-side space is filled therewith, the excess water overflows and is discharged through a washing pipeline. After the water feeding is conducted for a given time period, the water feed step is terminated.
  • CEB chemical-enhanced backwashing
  • aqueous solution of a chemical agent such as hydrochloric acid, sulfuric acid, nitric acid, citric acid, oxalic acid, ascorbic acid, sodium hydrogen sulfite, sodium hydroxide, or sodium hypochlorite.
  • oxidizing agents such as sodium hypochlorite are effective in removing organic-containing contaminants present in seawater, river water, water obtained by sewage or wastewater treatment, etc.
  • the concentration of sodium hypochlorite is preferably from 10 mg/L to 10,000 mg/L. This is because concentrations thereof less than 10 mg/L result in an insufficient detergent effect, while concentrations thereof higher than 10,000 mg/L result in an increase in the cost of the chemical agent and are uneconomical. A more preferred range of the concentration from these standpoints is from 100 mg/L to 5,000 mg/L.
  • the time period during which the membrane is kept in contact with the chemical is preferably about from 5 minutes to 3 hours. This is because too short contact periods result in insufficient detergency, while too long contact periods result in too long device operation suspension periods and a decrease in device operation efficiency and are hence uneconomical.
  • the separation membrane device may be configured so that, although not shown in the drawing, a pump or the like is disposed on the downstream side of the immersion type separation membrane to suck the raw water in order to filter the raw water with the immersion type separation membrane or so that the liquid level in the permeate tank is lower than the liquid level in the raw-water tank in order to conduct the filtration using a difference in water head pressure as a driving force.
  • a common operation sequence includes a filtration step and a suspension step, and the device is generally operated while continuously preforming the air washing with the air blower during both steps so that the suspended substances which have accumulated in the filtration step are removed from the membrane surface in the suspension step.
  • the membrane used in a membrane element constituting the immersion type separation membrane is not particularly limited, and may be either a flat membrane or a hollow-fiber membrane.
  • the structure of the membrane is not particularly limited, and any of the following may, for example, be used: a flat-membrane element structure; a flat-membrane element structure including a flat membrane which has been spirally wound; a flexible flat-membrane element structure that includes a pair of flat membranes disposed so that the permeate-side surfaces thereof face each other and having a water collection channel disposed therebetween and further includes a sealing part which seals peripheral portions of the flat membranes; and a hollow-fiber membrane element structure including a bundle of a plurality of hollow-fiber membranes.
  • the second separation membrane to which the present invention is applied examples include a reverse osmosis membrane (not shown).
  • the pressure of the raw water to be treated is elevated by a high-pressure pump for feeding the raw water to the reverse osmosis membrane, and the pressurized raw water is separated by the reverse osmosis membrane into a permeate and a concentrate.
  • Disposed on the discharge side of the high-pressure pump is either a feed flow rate control valve, which is for controlling the feed flow rate of the raw water discharged from the high-pressure pump and to be fed to the reverse osmosis membrane, or an inverter, which controls the frequency of the high-pressure pump to control the feed flow rate of the raw water being discharged from the high-pressure pump.
  • a concentrate flow rate control valve for controlling the concentrate flow rate is disposed.
  • the second separation membrane device is generally operated while controlling the flow rates of the feed water and concentrate.
  • the reverse osmosis membrane is disposed in the device after having been processed into a reverse osmosis membrane element.
  • a reverse osmosis membrane element examples thereof include: a spiral element obtained by winding a flat membrane around a water collection tube; a plate-and-frame element obtained by bonding flat membranes to both surfaces of a supporting plate and stacking such structures at regular intervals with spacers disposed therebetween to constitute a module; a tubular element employing a tubular membrane; and a hollow-fiber membrane element obtained by bundling hollow-fiber membranes and disposing the bundle in a case.
  • any of these element forms may be employed, it is preferred to use the spiral element from the standpoints of operation efficiency and interchangeability. The number of elements can be set at will in accordance with the membrane performance.
  • a membrane which includes a dense layer in at least one surface thereof and which has pores so that the pore diameter increases gradually from the dense layer toward an inner portion of the membrane or toward the other membrane surface; or a membrane (composite membrane) including such an asymmetric membrane and, formed on the dense layer thereof, a very thin separation functional layer constituted of another material.
  • composite membranes are preferred from the standpoint of attaining a high fresh-water production rate.
  • polyamide-based composite membranes, in particular piperazine-polyamide-based composite membranes are preferred from the standpoints of permeate flow rate, chemical resistance, etc.
  • the fresh-water production apparatus was described above in which the first separation membrane was a microfiltration membrane or an ultrafiltration membrane and the second separation membrane was a reverse osmosis membrane.
  • the fresh-water production apparatus may be configured so that the first separation membrane is a microfiltration membrane and the second separation membrane is an ultrafiltration membrane or that the first separation membrane is a reverse osmosis membrane capable of accommodating high salt concentrations and the second separation membrane is a reverse osmosis membrane capable of accommodating low salt concentrations.
  • the fresh-water production apparatus may employ any of settling/floatation separation, an anaerobic treatment method, a sand filtration method, an ion exchange method, a physical adsorption method, and an oxidation/disinfection method in combination with the first water treatment method and second water treatment method or may include any of those water treatment methods arranged in two or more stages.
  • a fresh-water production apparatus in which the first water treatment method is a sand filtration method and the second water treatment method is a membrane separation method employing a microfiltration membrane
  • a fresh-water production apparatus in which the first water treatment method is a membrane separation method employing a reverse osmosis membrane and the second water treatment method is an ion exchange method.
  • the present invention hence relates to a method of controlling a fresh-water production apparatus on the basis of a prediction of filtration characteristics, and this method is characterized by including the following steps, which are shown in FIG. 2 .
  • This method is for controlling a fresh-water production apparatus, such as that shown in FIG. 1 , in which raw water to be treated is treated by an (n ⁇ 1)-th stage water treatment method and the treated water obtained by the (n ⁇ 1)-th stage water treatment method is further treated by an n-th stage water treatment method, and is a fresh-water production method characterized by including a filtration-characteristic prediction step 12 for the (n ⁇ 1)-th stage water treatment method, in which filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from predicted input condition 11 for the (n ⁇ 1)-th stage water treatment method, a filtration-characteristic prediction step 22 for the n-th stage water treatment method, in which filtration characteristic of the n-th stage water treatment method is predicted from predicted input condition 21 for the n-th stage water treatment method, a filtration-characteristic deviation assessment step 13 for the (n ⁇ 1)-th stage water treatment method, in which a deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and filtration characteristic of
  • the method described above is for the case where a deviation has occurred in the (n ⁇ 1)-th stage water treatment method with respect to the filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method and the filtration characteristic of the (n ⁇ 1)-th stage water treatment method.
  • the fresh-water production method includes a filtration-characteristic prediction step 22 for the n-th stage water treatment method, a filtration-characteristic deviation assessment step 23 for the n-th stage water treatment method, in which a deviation of filtration characteristic of the n-th stage water treatment method is assessed, a cyclic prediction calculation step 24 for the n-th stage water treatment method, in which in cases when a deviation of the filtration characteristic of the n-th stage water treatment method has occurred, the predicted input condition 21 for the n-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the n-th stage water treatment method and filtration characteristic of the n-th stage water treatment method decreases to or below a specified value, a control condition recording step 25 for the n-th stage water treatment method, in which control condition for the n-th stage water treatment method is determined from final input condition obtained in the cyclic prediction calculation step 24 for the n-th stage water treatment method and is recorded,
  • the predicted input condition 11 for the (n ⁇ 1)-th stage water treatment method and the predicted input condition 21 for the n-th stage water treatment method are not limited.
  • examples thereof include filtration-step period and filtration rate in the fresh-water production apparatus as shown in Table 1.
  • the examples include the period of each physical washing step and flow rate in each step, combination of steps for physical washing, the period of each CEB step and flow rate in each step, and combination of steps in CEB step.
  • the examples include the period of each filtration or suspension step and flow rate in an air washing step.
  • the examples include methods for injecting a chemical, e.g., a scale inhibitor or a bactericide, such as the concentration of the injected chemical and the period of injection, and intervals for a flushing step and the period and strength thereof.
  • a chemical e.g., a scale inhibitor or a bactericide
  • Input condition change items for the case where filtration- characteristics deviation has occurred in physical washing step Index of raw-water property regarding x ⁇ physical washing step Period of each physical washing step and ⁇ ⁇ Period is acquirable on-line as control flow rate in each step conditions but flow rate depends on equipment with on-line meter.
  • Input condition change items for the case where filtration- characteristics deviation has occurred in CEB step Index of raw-water property regarding x ⁇ CEB step Period of each CEB step and flow rate in ⁇ ⁇ Period is acquirable on-line as control each step conditions but flow rate depends on equipment with on-line meter. 2.
  • examples of the flow rate in each step of physical washing shown in section 1.2 in Table 1 include backwashing flow rate and air-washing flow rate.
  • filtration characteristics are predicted in the filtration-characteristic prediction step 12 for the (n ⁇ 1)-th stage water treatment method and the filtration-characteristic prediction step 22 for the n-th stage water treatment method. It is also possible, for example, to draw an approximate line from changes in filtration characteristics over time to predict filtration characteristics.
  • the separation membrane is a microfiltration membrane or an ultrafiltration membrane
  • use may be made of a method in which the rate of filtration resistance increases during a filtration step or the rate of irreversible filtration resistance remaining unremoved by physical washing is used as a parameter to predict filtration characteristics while taking account of predicted input conditions also.
  • filtration characteristics may be predicted from day-average filtration characteristics.
  • filtration-characteristic deviation assessment step 13 for the (n ⁇ 1)-th stage water treatment method and the filtration-characteristic deviation assessment step 23 for the n-th stage water treatment method use may be made of a method in which a specified value is set and in cases when the difference has increased to or above the specified value, it is deemed that a deviation has occurred, or a method in which moving averages of changes over time or a rate of change with the lapse of time is examined to assess a deviation.
  • control condition recording step 15 for the (n ⁇ 1)-th stage water treatment method and/or the control condition recording step 25 for the n-th stage water treatment method is more preferable that these control elements are arranged in the order of preference by reference to a control history and are controlled in the descending order of possible effectiveness.
  • the predicted input conditions shown above include uncontrollable items.
  • the quality of the raw water to be treated cannot be controlled, and even with any water quality, it is necessary to calculate a factor for control so that no deviation from an initial predicted value occurs.
  • Controllable factors are shown in Table 2 with respect to the case where the water treatment methods are membrane separation methods, as an example. It is necessary to employ different control conditions, among those, in accordance with the kind of the membrane to be used as the separation membrane.
  • control conditions for the (n ⁇ 1)-th stage water treatment method are at least any of the following A to C, and when the separation membrane employed in the n-th stage water treatment method is a reverse osmosis membrane, then the control conditions for the n-th stage water treatment method are at least any of the following F to I:
  • F at least any of feed-water flow rate, concentrate flow rate, and permeate flow rate, or recovery;
  • G ratio between rates of upstream and downstream permeate discharge (in the case of splitting);
  • Preference for Preference for Preference Preference maintaining maintaining for for for Preference intervals for intervals for product- product- electric- for separation separation water water power chemical membrane membrane Control items amount quality cost cost washing replacement Remarks 1.
  • the separation membrane is microfiltration membrane or ultrafiltration membrane
  • Period of filtration step ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ and flow rate therein Circulation rate (in the case ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ Cross-flow of cross flow filtration) circulation rate is controlled in the case of cross flow filtration.
  • Period of each physical ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ washing step/CEB step the number of steps, flow rate in each washing, combination of each step, concentration of injected cleaning chemical 2.
  • the separation membrane is reverse osmosis membrane
  • Concentration of injected ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ scale inhibitor, bactericide, pH regulator, or reducing agent in feed water Flow rate and pressure in ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ physical washing (flushing) and period and frequency thereof *
  • a general method in the case of a reverse osmosis membrane is to fabricate a module of the reverse osmosis membrane, charge a plurality of such modules into a pressure vessel, and operate the device.
  • any succeeding reverse osmosis membrane module is higher in the salt concentration of the raw water than the preceding reverse osmosis membrane module and is higher also in the salt concentration of the permeate accordingly.
  • the permeate is discharged both before (feed-water side) and after (concentrate side) the pressure vessel and the amounts of the permeate thus discharged before and after the pressure vessel are controlled to keep the overall salt concentration of the permeate constant. It is preferable that the amounts of the permeate thus discharged before and after the pressure vessel are controlled so that there is no deviation from an initial predicted value.
  • the present invention preferably includes an operation mode as shown in FIG. 3 .
  • the operation mode is preferably any of “preference for product-water amount”, “preference for product-water quality”, “preference for electric-power cost”, and “preference for chemical cost”.
  • the water treatment method is a membrane separation method
  • the fresh-water production apparatus has an operation mode selection step 32 in which any of those operation modes can be selected and one or more control items are controlled for each selected operation mode as shown in Table 2.
  • control ranges of the control items are set beforehand for each operation mode.
  • the filtration characteristic is at least any of differential pressure, pure-water permeability, and salt permeability.
  • a water treatment method which is a membrane separation method and the separation membrane is a reverse osmosis membrane
  • the factors to be calculated in the fresh-water production method may be a prolongation of filtration period or a reduction of the period of physical washing and CEB in the case where the (n ⁇ 1)-th stage water treatment method is, for example, a membrane separation method and the separation membrane is a microfiltration membrane or an ultrafiltration membrane. Controlling these factors in accordance with the present invention makes it possible to increase the amount of product water and reduce the power cost and chemical cost necessary for physical washing and CEB.
  • this cyclic prediction calculation step gives final input conditions including an item which is a trouble factor, thereby making it possible to assess a trouble by the present invention.
  • Use may be made of a method in which: the filtration-characteristic deviation assessment step is conducted multiple times; a cyclic calculation is made to calculate multiple sets of predicted input conditions at which a deviation of the filtration characteristic is not higher than a specified value; and those sets of predicted input conditions are deemed to be trouble factors. It is more preferable that these trouble factors are arranged in the order of preference by reference to a trouble history and are deemed to be a trouble in the descending order of possible trouble.
  • examples of the flow rate in each step of physical washing shown in section 1.2 in Table 1 include backwashing flow rate and air-washing flow rate.
  • backwashing flow rate and air-washing flow rate.
  • air-washing flow rate there are cases where no on-line meter has been disposed therefor, making it impossible to acquire operation data on-line. Because of this, if either of these flow rates is low for some reason, a deterioration in filtration characteristics occurs and a deviation from predicted filtration characteristics occurs.
  • the accuracy of trouble assessment can be improved by conducting trouble assessment while preferentially changing predicted input condition which is being unable to be acquired on-line and is acquired off-line rather than predicted input condition which is being acquired on-line.
  • a trouble factor which has been extracted by trouble assessment may be regarded as an abnormality to output an alarm. It is preferable that alarms for abnormalities can be outputted in stages, and the alarms may be given by utilizing a noticing means, e.g., mails. Furthermore, by controlling items extracted by trouble assessment, the fresh-water production apparatus can be stably operated.
  • the (n ⁇ 1)-th stage water treatment method is a membrane separation method in which the separation membrane is an ultrafiltration membrane and the n-th stage water treatment method is a membrane separation method in which the separation membrane is a reverse osmosis membrane.
  • That the period of each step of physical washing is prolonged means that the proportion of filtration steps decreases, in the device including an ultrafiltration membrane, which is operated while repeating a filtration step and a physical washing step. That is, the amount of water filtered with the separation membrane in the (n ⁇ 1)-th stage water treatment method decreases.
  • predicted input condition for the separation membrane of the n-th stage water treatment method is changed and whether a change in the recovery results in a deviation from initial predicted filtration characteristic or not is assessed in the cyclic prediction calculation step 24 for the n-th stage water treatment method.
  • the cyclic calculation is terminated and the control condition is stored in the control condition recording step 25 for the n-th stage water treatment method.
  • both the separation membrane of the (n ⁇ 1)-th stage water treatment method and the separation membrane of the n-th stage water treatment method can be stably operated while attaining the preference for product-water amount selected in the operation mode selection step 32 .
  • That the concentration of the injected chemical is increased means an increase in the cost of the chemical used for the reverse osmosis membrane of the n-th stage water treatment method. Furthermore, in cases when the preference for chemical cost given in Table 2 has been selected in the operation mode selection step 32 , it is necessary, for compensating for the increase in chemical cost for the separation membrane of the n-th stage water treatment method, to reduce the concentration of a chemical to be injected in CEB steps or physical washing steps for the separation membrane of the (n ⁇ 1)-th stage water treatment method.
  • predicted input condition for the separation membrane of the (n ⁇ 1)-th stage water treatment method is changed and whether a reduction in the chemical concentration results in a deviation from initial predicted filtration characteristic or not is assessed in the cyclic prediction calculation step 14 for the (n ⁇ 1)-th stage water treatment method.
  • the cyclic calculation is terminated and the control condition is stored in the control condition recording step 15 for the (n ⁇ 1)-th stage water treatment method.
  • both the separation membrane of the (n ⁇ 1)-th stage water treatment method and the separation membrane of the n-th stage water treatment method can be stably operated while attaining the preference for chemical cost selected in the operation mode selection step 32 .
  • influences of the change in predicted condition may be determined with an empirical formula or from actual results. It is more preferable that influences of changes in predicted input condition in the fresh-water production apparatus to which the present invention is applied are recorded beforehand and input condition is changed by reference to the record.
  • water treatment methods which are membrane treatment methods are as follows.
  • the filtration-step period and flow rate for the separation membrane of the (n ⁇ 1)-th stage water treatment method are controlled and the circulation rate, in the case of a cross flow operation, is controlled, thereby improving the quality of the water to be fed to the n-th stage separation membrane, and the quality of the water produced with the separation membrane of the n-th stage water treatment method (permeate quality) is also improved accordingly.
  • an improvement in product-water quality is attained, for example, by changing the upstream and downstream permeate discharge rates by increasing the rate of discharge from an upstream portion, where the feed water has a low salt concentration and the permeate has a low salt concentration, and reducing the rate of discharge from a downstream portion.
  • the cost of electric power for the backwashing pump, etc. can be reduced by reducing the period of and flow rates in physical washing steps for the separation membrane of the (n ⁇ 1)-th stage water treatment method.
  • a reduction in electric-power cost can be attained, for example, by reducing the recovery, since a reduction in recovery makes it possible to lower the pressure for water supply to the separation membrane of the n-th stage water treatment method, i.e., the feed pressure for the high-pressure pump.
  • the amount of foulants accumulating on the separation membrane of the (n ⁇ 1)-th stage water treatment method during filtration steps can be reduced by reducing the period of and flow rates in filtration steps, thereby making it possible to maintain intervals for washing of the separation membrane.
  • the flow rate in separation membrane washing is increased to enhance the physical washing, thereby discharging the foulants by the physical washing.
  • intervals for the washing of the separation membrane can be maintained.
  • the separation membrane of the (n ⁇ 1)-th stage water treatment method can be made less apt to suffer chemical deterioration, for example, by reducing the concentration of a cleaning chemical to be injected during a CEB step.
  • the separation membrane of the n-th stage water treatment method also can be made less apt to suffer chemical deterioration by reducing the concentration of a bactericide or pH regulator in the feed water, thereby prolonging the intervals for replacing the separation membrane.
  • the present invention relates to a fresh-water production apparatus including a combination of an (n ⁇ 1)-th stage water treatment method and an n-th stage water treatment method. It is more preferable that the present invention is applied to a flow in which each of water treatment methods mutually affect as shown below.
  • the (n ⁇ 1)-th stage water treatment method is a membrane separation method in which the separation membrane is a microfiltration membrane and the n-th stage water treatment method also is a membrane separation method in which the separation membrane is a reverse osmosis membrane.
  • the present patent is employed in such a flow in which the treated water obtained in the (n ⁇ 1)-th stage water treatment method and that obtained in the n-th stage water treatment method affect the operation performance in each method in the whole fresh-water production apparatus.
  • the trouble assessment method may be in the form of a computer-readable program as shown in FIG. 4 , and the program may be stored in a computer-readable storage medium, which may be utilized in an operation control device 41 to operate a fresh-water production apparatus 7 .
  • the program 44 can be recorded in a storage medium 43 , e.g., a hard disk, of a computer 42 or in a storage medium of a control system, e.g., a PLC or a DCS, which is usually provided to fresh-water production apparatuses.
  • Operation data may be taken out of the control system via the internet using a remote monitoring device and stored in a storage medium of either an on-premise server, which is installed in any desired place, or a cloud server.
  • FIG. 4 shows an operation program for causing a computer to operate a fresh-water production apparatus 7 on the basis of predicted filtration characteristic.
  • the operation program is characterized by including the following steps.
  • the operation program is for operating a fresh-water production apparatus and is for executing the following steps: a filtration-characteristic deviation assessment step for an (n ⁇ 1)-th stage water treatment method, in which a deviation between predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and filtration characteristic of the (n ⁇ 1)-th stage water treatment method is assessed; a cyclic prediction calculation step for the (n ⁇ 1)-th stage water treatment method, in which in cases when a deviation has occurred in the filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method, the predicted input condition for the (n ⁇ 1)-th stage water treatment method is changed and a prediction calculation is repeated until the deviation between the predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and filtration characteristic of the (n ⁇ 1)-th stage water treatment method decreases to or
  • the operation program shown above is for the case where the filtration-characteristic deviation assessment step for the (n ⁇ 1)-th stage water treatment method has assessed the occurrence of a deviation in the (n ⁇ 1)-th stage water treatment method.
  • this can be handles with an operation program for the fresh-water production apparatus, which is for executing the following steps: a filtration-characteristic prediction step for the (n ⁇ 1)-th stage water treatment method, in which filtration characteristic of the (n ⁇ 1)-th stage water treatment method is predicted from predicted input condition for the (n ⁇ 1)-th stage water treatment method; a filtration-characteristic prediction step for the n-th stage water treatment method, in which filtration characteristic of the n-th stage water treatment method is predicted from predicted input condition for the n-th stage water treatment method; a filtration-characteristic deviation assessment step for the n-th stage water treatment method, in which a deviation between the predicted filtration characteristic of the n
  • More preferred in the present invention is an operation program for the fresh-water production apparatus which is for executing: a step for changing input condition for predicted filtration characteristic of the (n ⁇ 1)-th stage water treatment method and/or a step for changing input condition for predicted filtration characteristic of the n-th stage water treatment method, on the basis of an operation mode, e.g., any of the operation modes shown in Table 2, selected by an operation mode selection means; and a control step in which the fresh-water production apparatus is controlled on the basis of the control condition recording step for the (n ⁇ 1)-th stage water treatment method and the control condition recording step for the n-th stage water treatment method.
  • an operation mode e.g., any of the operation modes shown in Table 2
  • control condition to be recorded in the control condition recording steps is selected in accordance with the kinds of the separation membranes used; for example, in cases when the separation membrane in the (n ⁇ 1)-th stage water treatment method is a microfiltration membrane or an ultrafiltration membrane, then the control condition for the (n ⁇ 1)-th stage water treatment method is at least any of the following A to C, and in cases when the separation membrane in the n-th stage water treatment method is a reverse osmosis membrane, then the control condition for the n-th stage water treatment method is at least any of the following F to I:
  • F at least any of feed-water flow rate, concentrate flow rate, and permeate flow rate, or recovery;
  • G ratio between rates of upstream and downstream permeate discharge (in the case of splitting);

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
US17/798,982 2020-02-14 2021-02-12 Method for controlling fresh water generation apparatus by estimating filtration property, method for determining presence of trouble in fresh water generation apparatus, fresh water generation apparatus, program for operating fresh water generation apparatus, program for determining presence of trouble in fresh water generation apparatus, and recording medium Pending US20230174390A1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP2020-023071 2020-02-14
JP2020023071 2020-02-14
JP2020-057377 2020-03-27
JP2020057377 2020-03-27
PCT/JP2021/005268 WO2021162093A1 (ja) 2020-02-14 2021-02-12 ろ過特性予測による造水装置の制御方法、造水装置のトラブル判定方法、造水装置、造水装置の運転プログラム、造水装置のトラブル判定プログラム、および記録媒体

Publications (1)

Publication Number Publication Date
US20230174390A1 true US20230174390A1 (en) 2023-06-08

Family

ID=77292736

Family Applications (1)

Application Number Title Priority Date Filing Date
US17/798,982 Pending US20230174390A1 (en) 2020-02-14 2021-02-12 Method for controlling fresh water generation apparatus by estimating filtration property, method for determining presence of trouble in fresh water generation apparatus, fresh water generation apparatus, program for operating fresh water generation apparatus, program for determining presence of trouble in fresh water generation apparatus, and recording medium

Country Status (4)

Country Link
US (1) US20230174390A1 (zh)
JP (1) JP7103513B2 (zh)
CN (1) CN115103820B (zh)
WO (1) WO2021162093A1 (zh)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7392877B2 (ja) * 2021-11-30 2023-12-06 東レ株式会社 分離膜エレメントの状態診断方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3520906B2 (ja) * 1999-08-27 2004-04-19 東レ株式会社 逆浸透膜プラントの運転方法、そのためのコンピュータ読取可能な記憶媒体、および記憶媒体を備えてなる逆浸透膜プラント
JP3900455B2 (ja) * 1999-11-05 2007-04-04 東レ株式会社 逆浸透膜装置とその運転方法、造水方法および制御装置
WO2009054506A1 (ja) * 2007-10-25 2009-04-30 Toray Industries, Inc. 膜ろ過予測方法、予測装置、及び膜ろ過予測プログラム
US9409110B2 (en) * 2011-07-14 2016-08-09 Nalco Company Method of maintaining water quality in a process stream
JP6049498B2 (ja) * 2013-02-25 2016-12-21 三菱重工業株式会社 逆浸透膜装置及びその運転方法
WO2017135235A1 (ja) * 2016-02-01 2017-08-10 三菱ケミカル株式会社 分離膜診断方法、水処理方法、分離膜診断装置、水処理装置及び分離膜診断プログラム

Also Published As

Publication number Publication date
CN115103820A (zh) 2022-09-23
JP7103513B2 (ja) 2022-07-20
CN115103820B (zh) 2024-02-09
WO2021162093A1 (ja) 2021-08-19
JPWO2021162093A1 (zh) 2021-08-19

Similar Documents

Publication Publication Date Title
US11141701B2 (en) Computer-readable recording medium on which clogging location specification program for separation membrane module is recorded, water production system, and water production method
EP2703066A1 (en) Method for cleaning membrane module
EP2633899A1 (en) Fresh water generation method and fresh water generation device
US20170274325A1 (en) Water treatment method
EP2633898A1 (en) Hollow fiber membrane filtration device and method for washing hollow fiber membrane module
JP5343655B2 (ja) 膜モジュールの運転方法
JPWO2016199725A1 (ja) 淡水製造装置および淡水製造装置の運転方法
US20230174390A1 (en) Method for controlling fresh water generation apparatus by estimating filtration property, method for determining presence of trouble in fresh water generation apparatus, fresh water generation apparatus, program for operating fresh water generation apparatus, program for determining presence of trouble in fresh water generation apparatus, and recording medium
JP6183213B2 (ja) 造水方法および造水装置
JP2016068046A (ja) 縦置き型外圧型中空糸膜モジュールおよびその運転方法
JPWO2017221984A1 (ja) 造水システムのトラブル判定プログラム及びトラブル判定装置、並びに記録媒体
JP5796419B2 (ja) 水処理方法及び水処理装置
EP4129455A1 (en) Method and program for determining cleaning trouble in fresh water generator
WO2019183221A1 (en) Chemical cleaning for membrane filters
US20170043298A1 (en) Method for operating clarifying-film module
JP2023096360A (ja) 水処理方法および水処理装置
US20230285904A1 (en) Method for operating separation membrane module, computer-readable recording medium having program recorded thereon, and water production system
CN113242758B (zh) 过滤装置及其运转方法
WO2023153026A1 (ja) 有機性排水の嫌気性処理方法及び装置
JP4804097B2 (ja) 水浄化システムの連続運転方法
JP2005279496A (ja) 膜分離装置の洗浄方法、膜分離方法および膜分離装置
JP2014195775A (ja) 中空糸膜モジュール
JP2003135936A (ja) 水処理方法および水処理装置
JP2017023969A (ja) 水処理システム及び水処理方法

Legal Events

Date Code Title Description
AS Assignment

Owner name: TORAY INDUSTRIES, INC., JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TOMIOKA, KAZUNORI;HAGAWA, KAZUKI;HAMADA, HIROSHI;SIGNING DATES FROM 20220531 TO 20220601;REEL/FRAME:061787/0330

STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION